[Acute cardiorenal syndromes]

Heart and kidney are closely interacting organs which function interdependently. Organ crosstalk between these two organs is based on humoral regulation and by inflammatory mediators, which are similar to those dominating systemic inflammation syndrome. The close interaction between heart and kidney results in organ dysfunction following both chronic and acute functional impairment of the respective counterpart. These changes are summarized under the term cardiorenal syndrome (CRS) which is subdivided into 5 types. In the setting of emergency medicine and intensive care units, CRS types 1 and 3 are the most common. CRS type 1 is characterized by acute kidney injury (AKI) developing as a consequence of acute heart failure. CRS type 3 is represented by acute cardiac failure following AKI, often occurring as a consequence of nephrotoxins. Diagnosis of CRS should preferably be made on basis of the Kidney Disease: Improving Global Outcomes (KDIGO) criteria for the diagnosis and staging of AKI. The cardiac diagnostic workup should include echocardiography, electrocardiogram (ECG), cardiac enzymes, and brain natriuretic peptide (BNP). The therapeutic approach in CRS is primarily aimed at treating the causative organ dysfunction. In case of CRS type 3 this means ensuring adequate kidney perfusion, cautious fluid management, and avoiding additional nephrotoxins. In case of diuretic resistant fluid overload, early initiation of extracorporeal fluid removal, preferably by renal replacement therapy, should be considered.